Reactive Streams 入門 #jjug

JJUG φΠτηϛφʔ:
Reactive Streams ೖ໳
Yuta Okamoto (@okapies)
2015/06/24

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Who are you?
• Ԭຊ ༤ଠ (@okapies)
• ւ֎ͷϚΠφʔͳ Scala OSS ͷൃ۷͕झຯ
• ʢγΣϧεΫϦϓτ৬ਓʣ
• Scala Matsuri 2016 ४උҕһʢ຋༁νʔϜʣ

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Scala Matsuri 2016
!
!
• དྷ೥1݄30ʙ31೔ʹ։࠵ܾఆʂ http://scalamatsuri.org/
• ४උҕһձͷελοϑืूதʂ
• ࣍ճఆྫ͸ 7/11ʢ౔ʣϦϞʔτࢀՃ࿮༗

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࡞ͬͨ΋ͷ
• ﬁnagle-kafka (https://github.com/okapies/
ﬁnagle-kafka)
• sircuit (https://github.com/okapies/sircuit)
• rx-process (https://github.com/okapies/rx-
process)

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ॻ͍ͨ΋ͷ
• ຋༁:
• Reactive Manifesto v2.0 (http://www.reactivemanifesto.org/ja)
• Effective Scala (http://twitter.github.io/effectivescala/index-ja.html)
• ໋ྩܕͷίʔϧόοΫɺؔ਺ܕͷϓϩϛε (https://gist.github.com/okapies/5354929)
• ϒϩάهࣄ (http://okapies.hateblo.jp/):
• ඇಉظετϦʔϜॲཧͷඪ४ԽΛ໨ࢦ͢ “Reactive Streams” ͱ͸
• ʮؔ਺ܕϓϩάϥϚͷͨΊͷ Rx ೖ໳ʯγϦʔζ
• ϚΠΫϩαʔϏε͕ Scala ΛબͿ̏ͭͷཧ༝
ࠓ೔ͷ͓୊ʂ

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Reactive 
Streams
https://www.ﬂickr.com/photos/vinothchandar/8160520014

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http://www.reactive-streams.org/announce-1.0.0 (2015/05/08)

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Reactive Streams ͱ͸ʁ
• ”Back-Pressure ෇͖ͷඇಉظετϦʔϜॲཧ“ͷඪ
४ΛఆΊΔ࢓༷
• ඇಉظετϦʔϜॲཧʹ͖ͭ·ͱ͏ϑϩʔ੍ޚ
ͷ՝୊ʢόοϑΝᷓΕ໰୊ʣͷղܾࡦΛఏࣔ
• ࢓༷ʹ४ڌͨ͠ϥϯλΠϜؒͷ૬ޓ઀ଓੑΛอ
ূ͢Δ
• ࠷ऴ໨ඪ͸ Java 9 Ͱͷඪ४Խ
ΤϯυϢʔβ޲͚ͷ 
API ͸είʔϓ֎ 
ʢ࣮૷ຖʹ༻ҙ͢Δʣ

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ओͳࢀՃϕϯμʔ
• (Akka)
• (RxJava)
• (Reactor)
• (Vert.x)
(Scala ݴޠͷ։ൃݩ)
(ถࠃ࠷େखͷ 
ಈը഑৴αʔϏε)

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ओͳࢀՃऀ
• Doug Lea
• JSR 166 (java.util.concurrent) 
ͷ Speciﬁcation Lead
• “Java Concurrency in Practice” 
ͷஶऀͷҰਓ
• ඪ४Խ͸ࢯͷओಋͰਐΊΒΕ͍ͯΔ
http://www.amazon.co.jp/dp/4797337206/

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ܦҢ
• Reactive Manifesto ͷൃද(2013೥9݄)
• Typesafe ͷओಋͰɺඇಉظετϦʔϜٕज़Λ
։ൃ͢Δϕϯμʔ֤ࣾͷؒͰɺϑϩʔ੍ޚͷٕ
ज़՝୊ͷղܾࡦΛ࿩͠߹͏ίϛϡχςΟ͕ൃ଍
• GitHub ʹ reactive-streams άϧʔϓΛ࡞੒ɻ
ਖ਼ࣜʹڞಉͰ࢓༷ࡦఆΛ࢝ΊΔ(2014೥ॳ಄)

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Reactive?
https://www.ﬂickr.com/photos/livenature/204420128

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Reactive ̋̋
 
ϓϩάϥϛϯάϞσϧ
!
ϥϯλΠϜ
!
ΞʔΩςΫνϟ
ʹ
×
×

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ࠓ೔ͷΩʔϫʔυ
Reactive Manifesto
Reactive Programming
Reactive Streams
ϓϩάϥϛϯάϞσϧ:
ϥϯλΠϜ:
ΞʔΩςΫνϟ:

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ࠓ೔ͷΩʔϫʔυ
Reactive Manifesto
Reactive Streams
ϥϯλΠϜ
ΞʔΩςΫνϟ

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Reactive
Programming
https://www.ﬂickr.com/photos/kovah/15331505770

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Ͳ͜Ͱ࢖ΘΕ͍ͯΔ͔
• GUIɾϑϩϯτΤϯυͷ࣮૷
• (ϚΠΫϩ)αʔϏεͷ࣮૷
• Ϗοάσʔλॲཧ
• etc… • Πϕϯτۦಈ
• ඇಉظϓϩάϥϛϯά
• ฒߦॲཧ
͕ඞཁͳͱ͜Ζશൠ

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ʊਓਓਓਓਓਓਓਓਓਓਓਓਓਓʊ
ʼ σʔλϑϩʔʴมߋͷ఻೻ ʻ
ʉY^Y^Y^Y^Y^Y^Y^Y^Y^Y^Yʉ
http://en.wikipedia.org/wiki/Reactive_programming
※ ఆٛͷҰྫͰ͢

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ී௨ͷ(खଓ͖ܕͷ)ίʔυ
A = 1;
B = 2;
C = (A+1) + (B-1)*2;
※”Ͳ͏΍࣮ͬͯߦ͢Δ͔”͸ࣗ໌
ʢʹ ࣮ߦϞσϧʣ

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σʔλϑϩʔ
g1
g2
h
Input
Input Output
f
ؔ਺
ೖྗ ग़ྗ
ؔ਺ͱɺؔ਺ಉ࢜Λܨ͗߹Θͤͨάϥϑ

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-1
×2
+
+1
A
B C
σʔλϑϩʔͰදͯ͠ΈΔ
A = 1;
B = 2;
C = (A+1) + (B-1)*2;
1
2 4
1 2
2
※Ͳ͏࣮ߦ͢Δ͔͸๨ΕΑ͏
ʢม਺ͱԋࢉࢠͷؔ܎͚ͩݟΔʣ

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-1
×2
+
+1
A
B C
ม਺Λߋ৽: खଓ͖ܕͷ৔߹
A = 1; B = 2;
C = (A+1) + (B-1)*2; 
A = 2;
1 $ 2
2 4
C ʹ͸ 
൓ө͞Εͳ͍
खଓ͖ܕͷ࣮ߦϞσϧ
×
×
×
×
× ×

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-1
×2
+
+1
A
B C
Reactive ͳมߋͷ఻೻
A := 1; B := 2; 
C := (A+1) + (B-1)*2; 
A := 2;
1 $ 2
4 $ 5
2
1 $ 3
1 2
A ͷมߋ͕ 
C ʹ൓ө͞ΕΔ
Reactive ͳ࣮ߦϞσϧ

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-1
×2
+
+1
A
B C
2
5 $ 7
2 $ 3
1 $ 2 2 $ 4
3
C := (A+1) + (B-1)*2; 
A := 2;
B := 3;
B ͷมߋ͕ 
C ʹ൓ө͞ΕΔ

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-1
×2
+
+1
A
B C
2 $ 0
7 $ 5
3
2 4
3 $ 1
A := 2; 
B := 3; 
A := 0;
A ͷมߋ͕ 
C ʹ൓ө͞ΕΔ

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Reactive Programming ͷ࣮ݱखஈ
1. ”σʔλϑϩʔ”Λ 
هड़͢ΔͨΊͷϓϩάϥϛϯάϞσϧ
2. ”มߋͷ఻೻”Λ 
ϓϩάϥϚʹ୅Θ࣮ͬͯߦ͢ΔϥϯλΠϜ

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ϓϩάϥϚ͔ΒݟΔͱ:
ؔ਺
ೖྗ ग़ྗ
1: ؔ਺
2: σʔλϑϩʔ 
ʢґଘؔ܎ͷάϥϑʣ
ͷೋͭΛ࢖ͬͯϓϩάϥϜΛهड़͢Δɻ
1
2
A
B C
f
g1
g2
+

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ྫ (RxJava):
Observable a = …;
Observable b = …;
!
Observable a1 = a.map( (i) -> i + 1 );
Observable b1 = b.map( (j) -> j - 1 )
.map( (k) -> k * 2 );
!
!
Observable c =
Observable.combineLatest(a1, b1,
(i, j) -> i + j );
A
B C
+1
—1
×2
+

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ྫ (RxJava):
Observable a = …;
Observable b = …;
!
Observable a1 = a.map( (i) -> i + 1 );
Observable b1 = b.map( (j) -> j - 1 )
.map( (k) -> k * 2 );
!
!
Observable c =
Observable.combineLatest(a1, b1,
(i, j) -> i + j );
σʔλϑϩʔΛܨ͛Δϝιου
ؔ਺
ೖྗ
A
B C
+1
—1
×2
+

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“What” ͱ “How” ͷ෼཭
ϓϩάϥϚ͸”ೖྗΛԿʹม׵͢Δ͔“͚ͩʹ 
஫໨ͯ͠ϩδοΫΛॻ͘ɻ
”Ͳ͏΍࣮ͬͯߦ͢Δ͔”͸ϥϯλΠϜͷ໾ׂɻ
ʢ࣮ߦϞσϧʣ
G
? ?
?
? ?
f
g1
+
g2

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Reactive ͳϞσϧͷϝϦοτ
• มߋ͕ࣗಈతʹ൓ө͞ΕΔ
• ඇಉظԽɾฒྻԽ͠΍͍͢
• ૊Έ߹ΘͤՄೳ (composable) ʹ͠΍͍͢
} ϥϯλΠϜʹ೚ͤΔ
(ੑೳ࠷దԽ΋༰қ)
ؔ਺
ೖྗ ग़ྗ
֤ؔ਺͸ೖྗͷΈʹ൓Ԡ͢Δ
→ ֎෦ͷঢ়ଶʹӨڹ͞Εͳ͍
→ ૄ݁߹ʹͳΔʂ

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༨ஊ: ΤΫηϧᄻ͑࿩ͱͷൺֱ
• Reactive Programming ͸“ΤΫηϧ”Ͱᄻ͑Δ
ΑΓσʔλϑϩʔϞσϧͰઆ໌͢Δํ͕ྑ͍
• composable ͳؔ਺ͷඞཁੑ͕෼͔Γқ͍
• ೖྗͱग़ྗͷґଘੑΛએݴͯ͠ϓϩάϥϛ
ϯά͢Δ΍Γํ͕ຊ࣭Ͱ͋Δ͜ͱΛࣔͤΔ

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͍Ζ͍Ζͳ 
https://www.ﬂickr.com/photos/deanhochman/12469727533

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RP ͷϓϩάϥϛϯάϞσϧ
• ໋ྩܕ Reactive Programming
• ΦϒδΣΫτࢦ޲ Reactive Programming (OORP)
• ؔ਺ܕ Reactive Programming (FRP)
• ͦͷଞʢFuture/PromiseɺActorʣ

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RP ͷϓϩάϥϛϯάϞσϧ
• ໋ྩܕ Reactive Programming
• ΦϒδΣΫτࢦ޲ Reactive Programming (OORP)
• ؔ਺ܕ Reactive Programming (FRP)
• ͦͷଞʢFuture/PromiseɺActorʣ
୯ʹ “RP” ͱݴ͏ͱ
͜Ε͕ଟ͍…ʁ
{

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ؔ਺ܕ Reactive Programming
• ਓʹΑͬͯࢦ͍ͯ͠Δ΋ͷ͕ҧ͏… ( ´-` )
• ຊདྷͷʢڱٛͷʣFRP
• ΧδϡΞϧͳʢ޿ٛͷʣFRP

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ຊདྷͷ FRP
• 1997 ೥ʹ Conal Elliott (@conal) Β͕ఏএ
• FRP ͷຊՈ͸ͬͪ͜Ͱɺݫີͳఆ͕ٛ͋Δ
Time
A
Behavior ≈ 
Function1[Time, A]
Event ≈
List>
࿈ଓతͳ
ʮ࣌ؒతʹมԽ͢ΔৼΔ෣͍ʯ
(t, a)
཭ࢄతͳ 
ʮΠϕϯτετϦʔϜʯ
A
Time
+

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ΧδϡΞϧͳ FRP
• ΠϕϯτετϦʔϜΛؔ਺ܕϓϩάϥϛϯάΛ׆༻͠ 
͏·͘ѻ͏ɺ͘Β͍ͷχϡΞϯε
• ੈͷதͰࠓɺΑ͘ݴٴ͞ΕͯΔ ”FRP” ͸େମͬͪ͜
(Rx, Bacon.js, Elm, …)
Time
A
Behavior ≈ 
Function1[Time, A]
Event ≈
List>
࿈ଓతͳ
ʮ࣌ؒతʹมԽ͢ΔৼΔ෣͍ʯ
(t, a)
཭ࢄతͳ 
ʮΠϕϯτετϦʔϜʯ
A
Time
+

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ͳͥ FRP ͳͷ͔ʁ
• σʔλϑϩʔΛએݴతʹॻ͚Δ
• ෭࡞༻Λ੍ݶ͢Δख๏ಉ࢜Ͱ૬ੑ͕ྑ͍
• ߴ֊ؔ਺ (map, fold, ﬁlter, …) ͷ׆༻
• ڱٛ΋޿ٛ΋ composability ΛߴΊΔखஈͱ
ͯؔ͠਺ܕͷख๏Λ࢖͍ͬͯΔ఺͸ಉ͡

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Future/Promise
• RP ͷ஥ؒʹೖΕΔ͜ͱ͕͋Δ
• σʔλϑϩʔ͸͋Δ͕มߋͷ఻೻͸ͳ͍
• ྺ࢙తʹ͸ 1970 ೥୅·ͰḪΔ͜ͱ͕Ͱ͖ɺRP
΍ Actor Ϟσϧͱ΋ਂ͍ؔ܎͕͋Δ
• JavaScript ͳͲͷϑϩϯτΤϯυͷ΄͔ɺϚΠΫ
ϩαʔϏεͷ࣮૷खஈͱͯ͠΋޿͘࢖ΘΕ͍ͯΔ
ʢTwitter Finagle ΍ Node.js ͳͲʣ

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Actor Ϟσϧ
• RP ͷ஥ؒʹೖΕͨΓೖΕͳ͔ͬͨΓ͢Δ
• ϓϩάϥϛϯάϞσϧతʹ͸ composablity ͕௿
͍ͷ͕೉఺
• ۙ೥͸ϥϯλΠϜͱͯ͠ͷଆ໘͕஫໨͞Ε͍ͯΔ
• Erlang ͕ఏএ͢Δ ”Let It Crash" ఩ֶʹجͮ͘଱ো
֐ੑɺෛՙ؅ཧɺεέʔϥϏϦςΟ
• Actor ϥϯλΠϜͷ্ʹ RP ͷϓϩάϥϛϯάϞσ
ϧΛࡌͤͨͷ͕ Akka Streamsʢޙड़ʣ

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Ϣʔεέʔεͱ࣮ྫ
https://www.ﬂickr.com/photos/sdstrowes/8248580877

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Ϣʔεέʔε
• GUIɾϑϩϯτΤϯυ
• ϚΠΫϩαʔϏε
• Ϗοάσʔλॲཧ

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GUIɾϑϩϯτΤϯυ
ྫ: RxJS
Ϛ΢εΫϦοΫͷετϦʔϜ͔Β 
μϒϧΫϦοΫ͚ͩΛநग़͢Δ
https://gist.github.com/staltz/868e7e9bc2a7b8c1f754
ΫϦοΫΛ 250ms 
͝ͱʹ·ͱΊͯ
ͦΕͧΕΛ 
௕͞ʹม׵͢Δ

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GUIɾϑϩϯτΤϯυ
https://github.com/tehmou/rx-android-architecture
RxJava + Android 
ͷσϞΞϓϦ
ςΩετϘοΫε͕ߋ৽͞Ε 
Δ౓ʹ JSON API Ͱݕࡧɻ
໭͖ͬͯͨ݁ՌΛඇಉظʹ
Widget ʹ൓ө

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ϚΠΫϩαʔϏε
val userAndTweets = Future.join(
userService.findByUserId(userId),
tweetService.findByUserId(userId)
)
find
find
userId userAndTweets
User 
Service
Tweet 
Service
http://www.slideshare.net/knoldus/finagle-by-twitter-engineer/16
join
ଞͷϚΠΫϩαʔϏε (UserService,
TweetService) ʹΫΤϦΛඇಉظʹ౤͛
ͯɺ݁Ռ͕ೋͭͱ΋ฦ͖ͬͯͨ࣌఺Ͱ 
ଋͶͯग़ྗ
ྫ: Twitter Finagle

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Ϗοάσʔλॲཧ
https://speakerdeck.com/googlecloudjapan/google-cloud-dataﬂowwoli-jie-suru
ྫ: Google Cloud Dataﬂow
PCollection Λม׵͢Δσʔλϑϩʔͱͯ͠هड़

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Ϗοάσʔλॲཧ
https://speakerdeck.com/googlecloudjapan/google-cloud-dataﬂowwoli-jie-suru
Google Ϋϥ΢υ͕ 
ϥϯλΠϜʹ͋ͨΔ
σʔλϑϩʔఆٛ

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͓·͚: Spark 1.4 ͷ 
DAG Visualization ػೳ
https://cloud.githubusercontent.com/assets/2133137/7625997/e0878f8c-f9b4-11e4-8df3-7dd611b13c87.png

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RP ͷීٴ͕΋ͨΒͨ͠΋ͷ
• ϓϩάϥϛϯάϞσϧͷ੔උ͕ਐΈɺඇಉظ
ॲཧ΍ฒߦॲཧͷෑډ͕େ෯ʹԼ͕ͬͨ
• ϞόΠϧ͔Βେن໛෼ࢄ؀ڥ·ͰɺϥϯλΠ
Ϝͷબ୒ࢶ΋ͲΜͲΜ૿͍͑ͯΔ
• UI ϓϩάϥϛϯάͷมֵ΍ɺϚΠΫϩαʔϏ
εͷ୆಄ͳͲΛޙԡ͠

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ࠓ೔ͷΩʔϫʔυ
Reactive Manifesto
Reactive Streams
ϓϩάϥϛϯάϞσϧ
ϥϯλΠϜ
ΞʔΩςΫνϟ:

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The Reactive
Manifest
http://www.reactivemanifesto.org/ja

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Reactive Manifesto ͱ͸
• ”Reactive Systems” ΁ͷࢧ࣋Λݺͼ͔͚Δจॻ
• Reactive ͳγεςϜ͕උ͑Δཁ݅ʹ͍ͭͯड़΂͍ͯΔ
• Typesafe ࣾ (Scala ݴޠͷ։ൃݩ) ͷϝϯόʔ͕ओಋ
• ͦͷଞʹ Dave Farley (”ܧଓతσϦόϦʔ”ͷஶऀ) ΍
Martin Thompson (ݩ LMAX CTO) ͳͲ
• ϚʔέςΟϯάจॻͱͯ͠ͷ৭࠼͕ೱ͍ʢํ޲ੑͱͯ͠
͸ “The Twelve-Factor App” ʹ͍͔ۙ΋ʣ

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γεςϜ΁ͷཁٻͷมԽ
਺೥લ ݱࡏ
αʔό਺ ʙ਺ेϊʔυ ਺ઍҎ্ʙ
ཁٻԠ౴࣌ؒ ʙ਺ඵ ʙϛϦඵ
ཁٻՔಇ཰
਺࣌ؒͷΦϑϥΠϯ 
ϝϯςφϯεΛڐ༰
100%
σʔλྔ ΪΨόΠτ୯Ґ ϖλόΠτ୯Ґ

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γεςϜͷ࡞ΓํͷมԽ
“େن໛γεςϜΛߏங͢Δ૊৫͸ 
͜ͷมԽʹରॲ͢ΔઃܭݪଇΛ 
͢Ͱʹൃݟ͍ͯ͠Δ”
!
!
!
“ͦͷΑ͏ͳಛ௃Λඋ͑ΔγεςϜΛ
Reactive Systems ͱݺ΅͏”

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Reactive Systems ͷಛ௃

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Reactive Systems ͷಛ௃
Ϣʔβ΁ਝ଎͔ͭ 
Ұ؏ͨ͠଎౓ͰԠ౴͢Δ
ো֐࣌ʹ΋ 
ଈԠੑΛҡ࣋͢Δ
ඇಉظϝοηʔδύογϯά͕ 
શͯͷج൫Ͱ͋Δ
ෛՙ͕มಈͯ͠΋ 
ଈԠੑΛҡ࣋͢Δ

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…۩ମతʹ͸ʁ
• ۩ମྫ͸ಛʹڍ͛ΒΕ͍ͯͳ͍
• Actor Ϟσϧ ʹجͮ͘ΞʔΩςΫνϟΛڧ
͘૝ఆ͍ͯ͠Δ
• ҰํͰϚΠΫϩαʔϏεͱ΋਌࿨ੑ͕ߴͦ
͏ʹݟ͑Δ

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Dave Farley ᐌ͘:
ࢲ͕࢓ࣄͰؔΘͬͨɺେ͖ͳγεςϜͷΞʔΩςΫνϟʹ͸ྨ
ࣅ఺͕͋ͬͨɻͦ͏ͨ͠γεςϜͰ͸ɺ໰୊ྖҬʹ͓͚Δ໌֬
ͳ Bounded Context Λ࣮૷ͨ͠αʔϏε͕ૄ݁߹Ͱ݁ͼ͍ͭ
͓ͯΓɺޓ͍ͷ௨৴͸ඇಉظϝοηʔδͷΈͰߦ͏ɻ͜ΕΒ
͸ɺRDB ͷ্ʹߏங͞Εͨശग़͠ͷඪ४తͳࡾ૚ΞʔΩςΫ
νϟͷγεςϜͷ΍Γํͱ͸ࣅͯ΋ࣅ͔ͭͳ͍ɻ
ιϑτ΢ΣΞΛ࣮ߦ͢Δϋʔυ΢ΣΞ؀ڥ͕มΘΓͭͭ͋Δɻ
RAM ͱσΟεΫͷՁ͕֨ࠩॖ·ΓɺRAM ༰ྔ͸ܶతʹ૿Ճɻ
ࠓ΍෼ࢄϓϩάϥϛϯά͸ඪ४ͰɺωοτϫʔΫ͸σΟεΫ
ΑΓ଎͍ɻେ༰ྔͷඇشൃੑ RAM ͷ࣮༻Խ͸ؒۙͩɻ͜Ε͸
ͭ·Γɺʮඪ४తΞϓϩʔνʯΛࢧ࣋͢ΔԾઆ͕มԽͨ͠ͱ
͍͏͜ͱͩɻ
“The Reactive Manifesto | Dave Farley's Weblog” ΑΓົ༁

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ਤʹ͢Δͱ:
ϓϨθϯςʔγϣϯ
ϏδωεϩδοΫ
RDB
ಉظݺग़
ಉظݺग़
RDB
ඇಉظ
ඇಉظ
ඇಉظ
֎෦ 
αʔϏε
ඇಉظ
ϚΠΫϩαʔϏε 
ͬΆ͘ݟ͑Δ

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STORAGE &
RETRIEVAL
LOGIC
PRESENTATION
ROUTING
Redis
Memcache
Flock
T-Bird
MySQL
Tweet
User
Timeline
Social
Graph
DMs
API
Web
Monorail
TFE
HTTP Thrift “Stuff”
http://monkey.org/~marius/scala2015.pdf
࣮ࡍͷϚΠΫϩαʔϏε 
(Twitter)

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ϚΠΫϩαʔϏε ⊂ RSʁ
• ϚΠΫϩαʔϏε͸ Reactive Systems ͷ۩ମ
ྫͷҰͭͩͱߟ͑ͯΑͦ͞͏
• ஶऀୡ΋ΠϯλϏϡʔ౳ͰϚΠΫϩαʔϏε
ͱͷؔ܎ʹݴٴ͍ͯ͠Δ[1][2]
[2]: http://www.infoq.com/jp/news/2014/11/thompson-reactive-manifesto-2
[1]: http://www.infoq.com/articles/reactive-programming-anti-patterns

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vs. Reactive Programming
• Reactive Manifesto ͸ Reactive Programming
͔Β༻ޠΛआΓ͖ͯͨผ෺ͱߟ͑Δͷ͕ྑ͍
• Reactive ͷʮ֎෦͔Βͷܹࢗʹ൓Ԡ͢Δʯͱ
͍͏ҙຯ߹͍Λڧௐ͍ͯ͠Δ 
ʢΠϕϯτɺෛՙɺো֐ɺϢʔβɺ…ʣ

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vs. Reactive Programming
• ͱ͸͍͑…ϝοηʔδۦಈʹΑΔඇಉظϓϩ
άϥϛϯά͕େલఏʹͳΔͷͰɺ࣮૷खஈͷ
Ұͭͱͯ͠ Reactive Programming ͸༗ྗ
Reactive Manifesto
Reactive
Programming
Callback-
based
…
???
ϓϩάϥϛϯά
Ϟσϧ
ϥϯλΠϜ
ΞʔΩςΫνϟ
Actor
Model

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Programming × Systems
• Reactive Manifesto ͷ໨ࢦ͢ੈք:
• େن໛σʔλΛѻ͑ΔεέʔϥϒϧͰՄ༻
ੑͷߴ͍෼ࢄγεςϜ
• RM ͷจ຺Ͱ RP Λ׆༻͢Δʹ͸ɺେن໛ॲཧ
ʹରͯ͠ responsive ͳϥϯλΠϜ͕ඞཁ

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ࠓ೔ͷΩʔϫʔυ
Reactive Manifesto
Reactive Streams
ϥϯλΠϜ:
ΞʔΩςΫνϟ:

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Reactive
Streams
https://www.ﬂickr.com/photos/jeremybrooks/3546105970

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Ϣʔεέʔε
• ԻָɾϏσΦͷετϦʔϛϯά
• ωοτϫʔΫΛհͨ͠όϧΫσʔλͷసૹ
• αʔό㱻ϞόΠϧΫϥΠΞϯτؒͷ௨৴
• IoT (Internet of Things)
• ϦΞϧλΠϜσʔλղੳॲཧ
• etc…

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Reactive Streams ͷਖ਼ମ
ඇಉظετϦʔϜॲཧ
!
Non-blocking
back pressure
+
↑͕͜͜ϙΠϯτʂ

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Reactive Streams ͷਖ਼ମ
2: https://www.ﬂickr.com/photos/jeremybrooks/3546105970
1: https://www.ﬂickr.com/photos/vinothchandar/8160520014
૊Έࠐ·Εͨ 
ϑϩʔ੍ޚ
ͩͩྲྀ͠
[·͕͍ͪ] [͍͔͍ͤ]

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ͩͩྲྀͩ͠ͱԿ͕Ϛζ͍ͷ͔
https://www.ﬂickr.com/photos/chiaralily/4978843623/
εύΠΫͨ͠σʔλ
զʑͷγεςϜ

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σʔλϑϩʔͷܾյ
• Publisher ͸ Subscriber ΁ϝοηʔδΛૹΔ
Publisher Subscriber
…
3 msgs/sec 3 msgs/sec
ϝοηʔδόοϑΝ
ॲཧೳྗ
ૹ৴ೳྗ
=

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σʔλϑϩʔͷܾյ
• Subscriber ͕଎͍ͱ͖͸ՋʹͳΔ 
→ ܭࢉػࢿݯΛ༗ޮ׆༻Ͱ͖ͳ͍
…
<
3 msgs/sec
དྷͳ͍…
͋Μ·ૹΔͱ 
ѱ͍͔ͳ…
1 msg/sec

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σʔλϑϩʔͷܾյ
• Publisher ͕଎͗͢ΔͱόοϑΝ͕ᷓΕͯࢮ͵
…
>
3 msgs/sec
100 msgs/sec
΍Ίͯʂ
Զʹ 
·͔ͤΖʔʂ

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Back-Pressure
• Publisher ͸ϦΫΤετ͞Εͨ෼͚ͩϝοηʔ
δΛૹΔ → ҆શ
…
100 msgs/sec
[Request(3)]
3 msgs/sec
࣍ɺ3 ݸ͍ͩ͘͞
͍͋Αʔ

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Back-Pressure
• Back-Pressure ͸఻೻͢Δ
• C ͕஗͘ͳͬͨΒ B, A ΋εϩʔμ΢ϯ͢Δ
B C
…
ࠓ͸͍͍Ͱ͢
A …
ࠓ͸͍͍Ͱ͢
͍͋Αʔ

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SPI ͷΠϯλϑΣʔε
public interface Publisher {
public void subscribe(Subscriber super T> s);
}
public interface Subscriber {
public void onSubscribe(Subscription s);
public void onNext(T t);
public void onError(Throwable t);
public void onComplete();
}
public interface Subscription {
public void request(long n);
public void cancel();
}
͢΂ͯ໭Γ஋ͳ͠ʹඇಉظ
ޠኮ͸ RxJava ͕ϕʔε

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࢓༷ॻͱTCK
• ϥϯλΠϜؒͷ૬ޓ઀ଓੑΛอূ͢Δ

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ओͳ࣮૷
• Akka Streams (Typesafe)
• Ratpack
• Reactor (Spring)
• RxJava (Netﬂix)
• Vert.x 3.0 (Red Hat)

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DB ΞΫηεϥΠϒϥϦͷ࣮૷
• Slick 3.0 a.k.a “Reactive Slick” (JDBC)
• ReactiveMongo
• Reactive Rabbit (AMQP)
• Reactive Kafka
• etc…

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ͳͥ Reactive ͳ DB Ξμϓλ͕ඞཁʁ
• ྫ͑͹ɺJDBC ͸ಉظ API ͳͷͰɺඇಉظͳ
ϑϨʔϜϫʔΫΛ࢖͍ͬͯͯ΋ worker thread
΁ͷॲཧͷҕৡΛࣗ෼Ͱॻ͘ඞཁ͕͋ͬͨ
• context switch ͷίετɺεϨου਺ʹԠ͡
ͨϝϞϦফඅɺεϨουؒ௨৴ͷϩοΫڝ߹
• ϫʔΧεϨου਺ͱɺDB ίωΫγϣϯϓʔϧ
ͷαΠζΛ”ਖ਼͘͠”ઃఆ͢Δඞཁ͕͋Δ

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͢΂͕ͯ Reactive ʹͳΔ
• Reactive ͳ DB Ξμϓλ͕ग़ἧͬͨ͜ͱͰɺ
ೖޱ͔Βग़ޱ·Ͱ Reactive Streams ४ڌͷ෦
඼Ͱ૊Έ্͛ΒΕΔΑ͏ʹͳͬͨ
AMQP
Rx 
Java
Akka Vert.x RDB
ྫ:

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Reactive Streams ͷࠓޙ
• Java 9 Ͱͷඪ४Խ (j.u.c.Flow)
• ೿ੜϓϩδΣΫτ
• JavaScritp Interface (reactive-streams-js)
• Network Protocol (reactive-streams-io)
• Reactive IPC (http://reactive-ipc.io)

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Akka 
Streams

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Akka Streams ͱ͸
• Akka Λϕʔεʹͨ͠ Reactive Streams ࣮૷ͷ
ͻͱͭ
• σʔλϑϩʔΛهड़͢Δܕ҆શͳ DSL Λఏڙ
͢ΔʢJava ˍ Scalaʣ
• কདྷతʹ͸ Play Framework ͷج൫ʹͳΔ༧ఆ

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جຊతͳߟ͑ํ
• σʔλϑϩʔ 
 
 
 
Λ Actor ౳Λ࢖ͬͯ۩ݱԽ (materialize) ͢Δ
• ૊Έ্͛ͨ FlowGraph ࣗମ͸ઃܭਤ (blueprint)
ͳͷͰɺ৭ʑͳ Source ΍ Sink Ͱ࢖͍ճͤΔ
Source Flow Sink

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ίʔυྫ (Scala)
implicit val system = ActorSystem()
implicit val mat = ActorFlowMaterializer()
!
val source = Source[Int](1 to 5)
val sink = Sink.foreach[Int](println)
!
source.map(_ * 2).runWith(sink)
Source ×2 Sink
Actor ͷ४උ
Materializer Λ࢖࣮ͬͯߦ

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FlowGraph DSL
val g = FlowGraph { implicit builder =>
import akka.stream.scaladsl.FlowGraphImplicits._
!
source ~> f1 ~> bcast ~> f2 ~> merge ~> f3 ~> sink
bcast ~> f4 ~> merge
}
Source
f2
Sink
f4
f1
Broadcast
f3
Merge

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Materializer ͷਐԽ
• ݱࡏͷ Materializer ͸ Akka Actor ༻ͷΈ
• FlowGraph Λ࣮ߦϓϥϯ (execution plan) ͱΈͳ
͢ͱɺ৭ʑͳ͜ͱΛ࣮ݱ͢Δ༨஍͕͋Γͦ͏
• άϥϑͷ࠷దԽ΍ݕূɺ݁ՌͷΩϟογϡ
• akka-cluster ͱ૊Έ߹Θͤͯ෼ࢄΫϥελରԠ
• ཧ۶্͸ Spark ରԠ΋Մೳ…ʂʁ

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·ͱΊ

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·ͱΊ
• ΋͸΍ฒߦॲཧ΍ඇಉظϓϩάϥϛϯάΛڪ
ΕΔඞཁ͸ͳ͍
• RP ͷීٴͱ͍͏ܗͰಓ۩͸੔͍ͭͭ͋Δ
• ༷ʑͳϢʔεέʔεͰ࣮ࡍʹ׆༻͞Εͯ੒Ռ
Λڍ͍͛ͯΔ

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·ͱΊ
• য఺͸͢ͰʹϥϯλΠϜ΍γεςϜΞʔΩςΫ
νϟ΁ҠΓͭͭ͋ΔͷͰ͸ͳ͍͔
• Reactive Streams ͕࡞Γग़͢ΤίγεςϜ 
→ ैདྷܕ Web ΞʔΩςΫνϟ΁ͷ௅ઓ
• ϥϯλΠϜͷੑೳɺ଱ো֐ੑɺӡ༻ੑ͕બ
ఆج४ͱͯ͠ΑΓॏཁʹ
ҰํͰʮԿͰॻ͔͘ʯ͸ 
ͲΜͲΜऔΓସ͑ՄೳʹͳΔʁ

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Thank you!

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Reactive Streams 入門 #jjug

Reactive Streams 入門 #jjug

Yuta Okamoto

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